Effect of CO2 on crystallization kinetics of poly(ethylene terephthalate)

The effect of CO2 on the isothermal crystallization kinetics of poly(ethylene terephthalate), PET, was investigated using a high-pressure differential scanning calorimeter (DSC), which performed calorimetric measurements while keeping the polymer in contact with pressurized CO2, It was found that the crystallization rate followed the Avrami equation with values of the crystallization kinetic constant dependent on the crystallization temperature and concentration of CO2 in PET. The presence of CO2 in the PET increased its overall crystallization rate. CO2 also decreased the glass transition temperature, T-g, and the melting temperature, T-m. As a result, the observed changes in crystallization rate caused by CO2 can be qualitatively predicted from the magnitude of T-g depression and that of the equilibrium melting temperature, T-m(o).